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71.
太钢(集团)有限公司矿业公司峨口铁矿是一个从20世纪60年代就开始开采的老矿区,经过长期开采储量已严重不足。为了延长矿山寿命,需要进一步扩大勘探范围,在原有矿山周边地区进行勘探。最初采用岩心勘探钻机进行常规回转钻进加套管护壁,历时3个月。在上部堆积体地层最大钻孔深度达到约20m,再也无法继续钻进,使勘探工作被迫停止。针对深厚堆积体地层钻孔施工遇到的具体困难,介绍了风动潜孔锤双管跟管钻进在工程施工中的应用,在对深厚堆积体地层进行分析的基础上,探讨进行深厚堆积体地层钻孔施工的工艺方法及技术措施;在钻孔结构基础上选择钻孔设备及钻孔机具的一般原则,对深厚堆积体地层的钻孔工程施工具一定指导意义。 相似文献
72.
Herwig Dejonghe Anne Mathieu Veronique De Bruyne Sven De Rijcke 《Celestial Mechanics and Dynamical Astronomy》1998,72(3):219-233
We argue that the temperature of the stellar phase is likely a monotically decreasing function of radius in the central regions
of elliptical galaxies with cusps. We show that it requires the presence of a central mass concentration. An estimate of its
minimum mass based on few parameters is given. This lower bound is consistent with current mass values of the central objects
in galaxies derived from detailed models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
73.
Martin G. Haehnelt Priyamvada Natarajan & Martin J. Rees 《Monthly notices of the Royal Astronomical Society》1998,300(3):817-827
We demonstrate that the luminosity function of the recently detected population of actively star-forming galaxies at redshift z = 3 and the B -band luminosity function of quasi-stellar objects (QSOs) at the same redshift can both be matched with the mass function of dark matter haloes predicted by standard variants of hierarchical cosmogonies for lifetimes of optically bright QSOs anywhere in the range 106 to 108 yr. There is a strong correlation between the lifetime and the required degree of non-linearity in the relation between black hole and halo mass. We suggest that the mass of supermassive black holes may be limited by the back-reaction of the emitted energy on the accretion flow in a self-gravitating disc. This would imply a relation of black hole to halo mass of the form M bh ∝ v 5 halo ∝ M 5/3 halo and a typical duration of the optically bright QSO phase of a few times 107 yr. The high integrated mass density of black holes inferred from recent black hole mass estimates in nearby galaxies may indicate that the overall efficiency of supermassive black holes for producing blue light is smaller than previously assumed. We discuss three possible accretion modes with low optical emission efficiency: (i) accretion at far above the Eddington rate, (ii) accretion obscured by dust, and (iii) accretion below the critical rate leading to an advection-dominated accretion flow lasting for a Hubble time. We further argue that accretion with low optical efficiency might be closely related to the origin of the hard X-ray background and that the ionizing background might be progressively dominated by stars rather than QSOs at higher redshift. 相似文献
74.
The broad X-ray iron line observed in many active galactic nuclei spectra is thought to originate from the accretion disc surrounding the putative supermassive black hole. We show here how to perform the analytical integration of the geodesic equations that describe the photon trajectories in the general case of a rotating black hole (Kerr metric), in order to write a fast and efficient numerical code for modelling emission line profiles from accretion discs. 相似文献
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It is known that a sharp decrease in the angular velocity of the accretion disk around a black hole could in principle produce a kinematic axisymmetric dynamo, in contrast to the classical situation described by Cowling's antidynamo theorem. Here the effect of a nontrivial poloidal velocity of the disk is studied, showing that a strong gradient of this velocity enhances the possibilities of a working dynamo. 相似文献
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查明浅表部地层地质条件,对多层及高层建筑均至关重要。针对目前上海地区,在运用小螺纹钻孔进行浅表部工程勘察中存在的一些问题,就其如何合理使用,作了若干方面的探讨。 相似文献